1. Field of the Invention
This invention relates to apparatus and methods for gathering electromagnetic radiation, measuring the direction to the source of the radiation, and analyzing the radiation. In some embodiments, optical components of the apparatus may be employed in solar power applications.
2. Description of Related Art
In recent years numerous instances of commercial aircraft being irradiated with laser beams have been reported. These often turn out to be the actions of pranksters, but the result may be distractions to the flight crew and, with sufficient power in the laser, eye damage to the flight crew. Incidents of laser distraction of pilots usually occur when the aircraft is upon approach to land, which is the most dangerous part of flight. Pilots may wish to take countermeasures to protect themselves from the effects of the laser beam. For military operations, offensive laser systems designed specifically to destroy pilot eyesight have been developed.
Many tactical weapon targeting systems, such as anti-aircraft, anti-tank, and anti-satellite systems use lasers to designate targets and/or determine range to a target. Lasers may be used to designate any type of target, including buildings, vehicles, military and civilian aircraft, spacecraft, and individual people. In some cases, laser irradiation may prevent imaging devices, like those for reconnaissance or security, from viewing a desired scene without being overloaded by the high-brightness laser source. In other cases, laser irradiation may be used to interfere with an optical communication system by either overloading optical detectors or by overpowering a legitimate signal with one containing interfering information. Furthermore, laser irradiation is often not apparent, as many lasers do not radiate in the visible portion of the light spectrum.
Targets of laser irradiation could benefit from the ability to detect and overcome such interferences when they are irradiated. A laser detection system can enable a potential target to take evasive action, deploy countermeasures, or employ protective measures. Current laser detectors are inefficient and inaccurate at detecting the location of interfering radiation source, necessitating a need for the use of multiple, expensive detectors. Furthermore, existing laser detection systems do not have the ability to determine whether a laser irradiating a craft is a danger requiring protective action or merely a nuisance to be ignored. A need exists for more accurate, efficient, and effective laser detector systems.
Dubois et al. (U.S. Pat. No. 5,428,215) and Cantin et al. (U.S. Pat. No. 5,604,695) disclose High Angular Resolution Laser Irradiation Detectors (HARLID) with a linear array of radiation detectors below shadow masks with a series of slots (Dubois) or transparent apertures (Cantin). The pattern of detectors that are or are not irradiated is used to determine the angle of radiation arrival. However, the resolution of these systems is low and dependent on using multiple detectors, such that obtaining even a rough position estimate of the radiation source is difficult. In addition, these devices are incapable of detecting laser irradiation arriving from across an entire hemisphere. Rather, they more easily detect radiation that arrives near to perpendicular to the detector surface and often fail to detect radiation that arrives at an angle closer to horizontal to the detector surface. Furthermore, these detectors are incapable of determining the wavelength of incoming radiation.
Thomas et al. (U.S. Pat. No. 7,196,301) disclose a laser detector that includes an array of lenses and an array of optic devices (including light sources and light detectors). To estimate the angle of radiation arrival, the lens is adjusted to determine the position at which energy from the incoming laser is maximized. Like the Dubois and Cantin devices, this detector is incapable of detecting laser irradiation arriving from across an entire hemisphere. The device has moving parts and a limited angular range, and is incapable of detecting the wavelength of incoming radiation, and lacks the capability to detect information placed on a laser beam via modulation.
A need remains for a laser detection system that can identify at least the wavelength and angle of arrival of laser radiation, that has the ability to decode modulated or pulsed light, and that is capable of functioning in any ambient light conditions (i.e., day or night). A radiation detector and analysis system with these capabilities could significantly enhance laser detection and eliminate the current necessity for multiple detectors under a variety of conditions.